How to Get Rid of Those Weird Marks on Your Lumber

I bought some lumber that has cup-shaped marks on its face. The guys behind the counter said it was all like that. What can I do about it?Mike S., Santa Monica, California

There are two options for how lumber emerges from a log and leaves the sawmill. It can be left as is, rough and damp, or processed to perfection—dry, smooth, flat, and straight. It sounds like you bought wood that is somewhere between the two.

The cup marks are caused by a rapid trip through a planer. To remove them, you'll need to run the boards through a benchtop planer. If you don't have one, they can be quite useful—and save you money. Check out our reviews of entry-level planers. We preferred the Ridgid R4331 ($370).

Begin by passing the lumber through the machine so its knives barely contact the wood surface. By making several semi-planed areas, you'll create a temporary flat reference face, giving you a continuous surface to run over the planer bed. Turn the board over and run the semi-planed surface against the planer bed, taking several light passes until the top of the board is smooth and straight. Flip the board again and use the newly straightened surface as the reference against the planer bed. Take a few more passes until both the top and bottom are smooth and straight.

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